Terminal apparatus, base station apparatus, communication method, and integrated circuit

ABSTRACT

The terminal apparatus receives a PHICH and a PDCCH, and in a case that transmission of a transport block corresponding to a first HARQ process and transmission of a transport block corresponding to a second HARQ process, each having a different processing time from reception of the PDCCH to transmission of a PUSCH, occur in an identical uplink subframe, an ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process.

TECHNICAL FIELD

The present invention relates to a terminal apparatus, a base station apparatus, a communication method, and an integrated circuit.

This application claims priority based on JP 2017-084698 filed on Apr. 21, 2017, the contents of which are incorporated herein by reference.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP) has been studying a radio access method and a radio network for cellular mobile communications (referred to as “Long Term Evolution (LTE)”, “Evolved Universal Terrestrial Radio Access (EUTRA)”, “Evolved Universal Terrestrial Radio Access Network (EUTRAN)”, and “New Radio”). A base station apparatus is also referred to as an evolved NodeB (eNodeB) or a gNodeB. A terminal apparatus is also referred to as a User Equipment (UE). In a cellular communication system, multiple areas are deployed in a cellular structure, with each of the multiple areas being covered by a base station apparatus. A single base station apparatus may manage a plurality of cells. In 3GPP, latency reduction enhancements have been studied. For example, for a solution for latency reduction, an effort has been started to reduce processing time with respect to a legacy (1 ms) Transmission Time Interval (TTI). (NPL 1)

There is a problem in that transmission of a PUSCH, by which the processing time is not shortened, required by a PHICH and transmission of the PUSCH, by which the processing time is shortened, scheduled by an uplink grant occur in the same uplink subframe. In this case, the 3GPP has been studying that the transmission of the PUSCH scheduled by the uplink grant is performed preferentially (NPL 2).

CITATION LIST Non Patent Literature

-   NPL 1: “Work Item on shortened TTI and processing time for LTE”,     RP-161299, Ericsson, 3GPP TSG RAN Meeting #72, Busan, Korea, Jun. 13     to 16, 2016. -   NPL 2: “Handling collisions between n+4 and n+3”, R1-1704633, ZTE,     ZTE Microelectronics, 3GPP TSG RAN WG1 Meeting #88bis, 3-7 Apr.     2017.

SUMMARY OF INVENTION Technical Problem

However, the transmission of the PUSCH required by the PHICH has not been fully studied.

An aspect of the present invention have been made in light of the foregoing, and an object of the present invention is to provide a terminal apparatus capable of efficiently communicating with a base station apparatus, an integrated circuit mounted in the terminal apparatus, a communication method used for the terminal apparatus, a base station apparatus for communicating with terminal apparatus, a communication method used for the base station apparatus, and an integrated circuit mounted in the base station apparatus.

Solution to Problem

(1) To accomplish the object described above, aspects of the present invention are contrived to provide the following measures. That is, a first aspect of the present invention is a terminal apparatus, the terminal apparatus including: a reception unit configured to receive a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and a transmission unit configured to perform, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process.

(2) A second aspect of the present invention is a base station apparatus for communicating with a terminal apparatus, the base station apparatus including: a transmission unit configured to transmit a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and a reception unit configured to receive, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process by the terminal apparatus.

(3) A third aspect of the present invention is a communication method used for a terminal apparatus, the communication method including the steps of: receiving a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and performing, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process.

(4) A fourth aspect of the present invention is a communication method used for a base station apparatus for communicating with a terminal apparatus, the communication method including the steps of: transmitting a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and receiving, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process by the terminal apparatus.

(5) A fifth aspect of the present invention is an integrated circuit mounted in a terminal apparatus, the integrated circuit including: a reception circuitry configured to receive a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and a transmission circuitry configured to perform, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process.

(6) A sixth aspect of the present invention is an integrated circuit mounted in a base station apparatus for communicating with a terminal apparatus, the integrated circuit causing the base station apparatus to perform: transmitting a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and receiving, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process by the terminal apparatus, and the transmission of the transport block corresponding to the second HARQ process is performed on the PUSCH.

Advantageous Effects of Invention

According to an aspect of the present invention, a terminal apparatus can efficiently communicate with a base station apparatus.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a radio communication system according to the present embodiment.

FIG. 2 is a diagram illustrating an example of a structure of a MAC layer for an uplink configured with carrier aggregation according to the present embodiment.

FIG. 3 is a diagram illustrating a schematic configuration of a radio frame according to the present embodiment.

FIG. 4 is a diagram illustrating an example of an uplink synchronous HARQ according to the present embodiment.

FIG. 5 is a diagram illustrating an example of an uplink asynchronous HARQ according to the present embodiment.

FIG. 6 is a diagram illustrating an example of PUSCH synchronous transmission by a PHICH according to the present embodiment.

FIG. 7 is a diagram illustrating an example of a collision of PUSCH transmission due to different processing time according to the present embodiment.

FIG. 8 is a diagram illustrating an example of a TTI and an sTTI according to the present embodiment.

FIG. 9 is a schematic block diagram illustrating a configuration of a terminal apparatus 1 according to the present embodiment.

FIG. 10 is a schematic block diagram illustrating a configuration of a base station apparatus 3 according to the present embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below.

FIG. 1 is a conceptual diagram of a radio communication system according to the present embodiment. In FIG. 1, a radio communication system includes terminal apparatuses 1A to 1C and a base station apparatus 3. The terminal apparatuses 1A to 1C are each referred to as a terminal apparatus 1.

Hereinafter, carrier aggregation will be described.

According to the present embodiment, at least one of multiple serving cells are configured for the terminal apparatus 1. A technology in which the terminal apparatus 1 communicates via the multiple serving cells is referred to as cell aggregation or carrier aggregation. An aspect of the present invention may be applied to each of the multiple serving cells configured for the terminal apparatus 1. Furthermore, an aspect of the present invention may be applied to some of the multiple serving cells configured. Furthermore, an aspect of the present invention may be applied to each of multiple serving cell groups configured. Furthermore, an aspect of the present invention may be applied to some of the plurality of serving cell groups configured. The multiple serving cells include at least one primary cell. The multiple serving cells may include at least one or more secondary cells. The multiple serving cells may include one or more Licensed Assisted Access (LAA) cells.

Time Division Duplex (TDD), Frequency Division Duplex (FDD), and/or Licensed Assisted Access (LAA) is applied to a radio communication system according to the present embodiment. For cell aggregation, FDD may be applied to all the multiple serving cells. For cell aggregation, TDD may be applied to all multiple serving cells. For cell aggregation, LAA may be applied to all the multiple serving cells. For cell aggregation, serving cells to which TDD is applied and serving cells to which FDD is applied may be aggregated. For cell aggregation, serving cells to which an LAA cell and FDD are applied may be aggregated. For cell aggregation, serving cells to which an LAA cell and TDD are applied may be aggregated.

The one or more serving cells configured include one primary cell and zero or more secondary cells. The primary cell is a cell in which an initial connection establishment procedure has been performed, a cell in which a connection re-establishment procedure has been initiated, or a cell indicated as a primary cell in a handover procedure. The secondary cell may be configured/added at a point of time when or after a Radio Resource Control (RRC) connection is established.

A carrier corresponding to a serving cell in the downlink is referred to as a downlink component carrier. A carrier corresponding to a serving cell in the uplink is referred to as an uplink component carrier. The downlink component carrier and the uplink component carrier are collectively referred to as a component carrier.

The terminal apparatus 1 can perform simultaneous transmission and/or reception on a plurality of physical channels in a plurality of serving cells (component carriers). A single physical channel is transmitted in a single serving cell (component carrier) out of the plurality of serving cells (component carriers).

FIG. 2 is a diagram illustrating an example of a structure of a MAC layer for an uplink configured with carrier aggregation according to the present embodiment. In the uplink configured with carrier aggregation, one independent HARQ entity exists for each serving cell (uplink component carrier). The HARQ entity manages multiple HARQ processes in parallel. The HARQ process is associated with an HARQ buffer. That is, the HARQ entity is associated with multiple HARQ buffers. The HARQ process stores MAC layer data in the HARQ buffer. The HARQ process indicates to a physical layer to transmit the MAC layer data.

In the uplink configured with carrier aggregation, at least one transport block may be generated for each of Transmission Time Intervals (TTIs) for each serving cell. Each of the transport blocks and HARQ retransmission of the transport block are mapped to one serving cell. The TTI is also referred to as a subframe. The transport block is MAC layer data transmitted on an uplink shared channel (UL-SCH).

In the uplink according to the present embodiment, the “transport block”, a “MAC Protocol Data Unit (PDU)”, “MAC layer data”, the “UL-SCH”, “UL-SCH data”, and “uplink data” are assumed to be the same.

Physical channels and physical signals according to the present embodiment will be described.

In uplink radio communication from the terminal apparatus 1 to the base station apparatus 3, the following uplink physical channels are used. The uplink physical channels are used for transmitting information output from a higher layer.

-   -   Physical Uplink Control CHannel (PUCCH)     -   Physical Uplink Shared CHannel (PUSCH)     -   Physical Random Access CHannel (PRACH)

The PUCCH is used to transmit Uplink Control Information (UCI). The uplink control information includes: downlink Channel State Information (CSI); a Scheduling Request (SR) used to request for a PUSCH (Uplink-Shared CHannel (UL-SCH) resource for initial transmission; and a Hybrid Automatic Repeat request ACKnowledgement (HARQ-ACK) for downlink data (a Transport block, a Medium Access Control Protocol Data Unit (MAC PDU), a Downlink-Shared CHannel (DL-SCH), or a Physical Downlink Shared CHannel (PDSCH)). The HARQ-ACK indicates an acknowledgement (ACK) or a negative-acknowledgement (NACK). The HARQ-ACK is also referred to as ACK/NACK, HARQ feedback, HARQ acknowledge, or HARQ control information.

The scheduling request includes a positive scheduling request or a negative scheduling request. The positive scheduling request indicates to request a UL-SCH resource for initial transmission. The negative scheduling request indicates not to request the UL-SCH resource for the initial transmission.

The PUSCH is used for transmission of uplink data (Uplink-Shared CHannel (UL-SCH)). Furthermore, the PUSCH may be used to transmit the HARQ-ACK and/or channel state information along with the uplink data. Furthermore, the PUSCH may be used to transmit only the channel state information. Furthermore, the PUSCH may be used to transmit only the HARQ-ACK and the channel state information.

Here, the base station apparatus 3 and the terminal apparatus 1 exchange (transmit and/or receive) signals with each other in their respective higher layers. For example, the base station apparatus 3 and the terminal apparatus 1 may transmit and/or receive RRC signaling in a Radio Resource Control (RRC) layer. The base station apparatus 3 and the terminal apparatus 1 may transmit and/or receive, in a Medium Access Control (MAC) layer, a MAC CE. Here, the RRC signaling and/or the MAC CE is also referred to as higher layer signaling. The RRC signaling and/or the MAC CE are/is included in a transport block.

In the present embodiment, “RRC signaling”, “RRC layer information”, “RRC layer signal” “RRC layer parameter”, “RRC message”, and “RRC information element” are assumed to mean the same thing.

The PUSCH is used to transmit the RRC signaling and the MAC CE. Here, the RRC signaling transmitted from the base station apparatus 3 may be signaling common to multiple terminal apparatuses 1 in a cell. The RRC signaling transmitted from the base station apparatus 3 may be signaling dedicated to a certain terminal apparatus 1 (also referred to as dedicated signaling). In other words, user device-specific (user device-unique) information is transmitted using the signaling dedicated to a certain terminal apparatus 1.

PRACH is used to transmit a random access preamble. The PRACH is used for indicating the initial connection establishment procedure, the handover procedure, the connection re-establishment procedure, synchronization (timing adjustment) for uplink transmission, and the request for the PUSCH (UL-SCH) resource.

The following uplink physical signal is used for uplink radio communication. The uplink physical signal is not used to transmit information output from the higher layer, but is used by a physical layer.

-   -   Uplink Reference Signal (UL RS)

The following downlink physical channels are used for downlink radio communication from the base station apparatus 3 to the terminal apparatus 1. The downlink physical channels are used for transmitting information output from the higher layer.

-   -   Physical Broadcast CHannel (PBCH)     -   Physical Control Format Indicator CHannel (PCFICH)     -   Physical Hybrid automatic repeat request Indicator CHannel         (PHICH)     -   Physical Downlink Control CHannel (PDCCH)     -   Enhanced Physical Downlink Control CHannel (EPDCCH)     -   Physical Downlink Shared CHannel (PDSCH)     -   Physical Multicast CHannel (PMCH)

The PBCH is used for broadcasting a Master Information Block (MIB, a Broadcast CHannel (BCH)) that is shared by the terminal apparatuses 1.

The PCFICH is used for transmission of information indicating a region (OFDM symbols) to be used for transmission of the PDCCH.

The PHICH is used for transmission of an HARQ indicator (HARQ feedback or response information) indicating an ACKnowledgement (ACK) or a Negative ACKnowledgement (NACK) for the uplink data (UpLink Shared CHannel (UL-SCH)) received by the base station apparatus 3.

The PDCCH and the EPDCCH are used to transmit Downlink Control Information (DCI). In the present embodiment, the “PDCCH” is assumed to include the “EPDCCH” for the sake of convenience. The downlink control information is also referred to as DCI format. The downlink control information transmitted on one PDCCH includes a downlink grant and HARQ information, or an uplink grant and HARQ information. The downlink grant is also referred to as a downlink assignment or a downlink allocation. The downlink assignment and the uplink grant are not transmitted together on one PDCCH. The downlink grant and the uplink grant may include HARQ information.

The downlink assignment is used for scheduling a single PDSCH within a single cell. The downlink assignment is used for scheduling the PDSCH within the same subframe as the subframe in which the downlink grant has been transmitted.

The uplink grant may be used for scheduling a single PUSCH within a single cell. The uplink grant may be used for scheduling a single PUSCH within a sequence of subframes succeeding the subframe in which the uplink grant has been transmitted.

The HARQ information may include a New Data Indicator (NDI) and information indicating a transport block size. The HARQ information transmitted on the PDCCH along with the downlink assignment also includes information indicating the number of the HARQ process in the downlink (downlink HARQ process Identifier/Identity, downlink HARQ process number). The HARQ information transmitted on the PDCCH with the uplink grant for an asynchronous HARQ may include information indicating the number of the HARQ process in the uplink (uplink HARQ process Identifier/Identity, uplink HARQ process number). The HARQ information transmitted on the PDCCH with the uplink grant for a synchronous HARQ need not include information indicating the number of the HARQ process in the uplink (uplink HARQ process Identifier/Identity, uplink HARQ process number).

The NDI indicates an initial transmission or retransmission. An HARQ entity indicates to a certain HARQ process to trigger the initial transmission in a case that the NDI provided by the HARQ information has been toggled relative to the value of the NDI for the transmission preceding the certain HARQ process. The HARQ entity indicates to a certain HARQ process to trigger the retransmission in a case that the NDI provided by the HARQ information has not been toggled as compared to the value of the NDI for the transmission preceding the certain HARQ process. Note that the HARQ process may determine whether NDI has been toggled.

The HARQ entity identifies the HARQ process to which the uplink grant and the HARQ information correspond, and passes the uplink grant and the HARQ information to the identified HARQ process. The HARQ process stores the uplink grant and the HARQ information passed from the HARQ entity.

Cyclic Redundancy Check (CRC) parity bits added to the downlink control information transmitted on one PDCCH are scrambled with a Cell-Radio Network Temporary Identifier (C-RNTI), a Semi Persistent Scheduling (SPS) C-RNTI, or a Temporary C-RNTI. The C-RNTI and the SPS C-RNTI are identifiers for identifying a terminal apparatus within a cell. The Temporary C-RNTI serves as an identifier for identifying the terminal apparatus 1 that has transmitted a random access preamble in a contention based random access procedure.

The C-RNTI and the Temporary C-RNTI are used to control PDSCH transmission or PUSCH transmission in a single subframe. The SPS C-RNTI is used to periodically allocate a resource for the PDSCH or the PUSCH.

Hereinafter, unless otherwise specified, the CRC parity bits added to the downlink control information according to the present embodiment are scrambled with the C-RNTI.

The PDCCH is transmitted on a PDCCH candidate. The terminal apparatus 1 monitors a set of PDCCH candidates in the serving cell. The set of PDCCH candidates is referred to as a search space. The search space includes at least a Common Search Space (CSS) and a UE-specific Search Space (USS). The UE-specific search space is derived at least from the value of the C-RNTI set by the terminal apparatus 1. That is, the UE-specific search space is separately derived for each terminal apparatus 1. The common search space is a search space common to the multiple terminal apparatuses 1, and is constituted by a Control Channel Element (CCE) with a predetermined index. The CCE includes multiple resource elements. The monitoring means an attempt to decode the PDCCH in accordance with a certain DCI format.

The PDSCH is used to transmit downlink data (Downlink Shared CHannel (DL-SCH)).

The PMCH is used to transmit multicast data (Multicast CHannel (MCH)).

The following downlink physical signals are used in the downlink radio communication. The downlink physical signals are not used to transmit the information output from the higher layer, but are used by the physical layer.

-   -   Synchronization signal (SS)     -   Downlink Reference Signal (DL RS)

The synchronization signal is used for the terminal apparatus 1 to establish synchronization in a frequency domain and a time domain in the downlink. In the TDD scheme, the synchronization signal is mapped to subframes 0, 1, 5, and 6 within a radio frame. In the FDD scheme, the synchronization signal is mapped to subframes 0 and 5 within a radio frame.

The downlink reference signal is used for the terminal apparatus 1 to perform channel compensation on a downlink physical channel. The downlink reference signal is used for the terminal apparatus 1 to obtain the downlink channel state information.

According to the present embodiment, the following five types of downlink reference signals are used.

-   -   Cell-specific Reference Signal (CRS)     -   UE-specific Reference Signal (URS) associated with the PDSCH     -   Demodulation Reference Signal (DMRS) associated with the EPDCCH     -   Non-Zero Power Chanel State Information-Reference Signal (NZP         CSI-RS)     -   Zero Power Chanel State Information-Reference Signal (ZP CSI-RS)     -   Multimedia Broadcast and Multicast Service over Single Frequency         Network Reference signal (MBSFN RS)     -   Positioning Reference Signal (PRS)

The downlink physical channels and the downlink physical signals are collectively referred to as a downlink signal. The uplink physical channels and the uplink physical signals are collectively referred to as an uplink signal. The downlink physical channels and the uplink physical channels are collectively referred to as a physical channel. The downlink physical signals and the uplink physical signals are collectively referred to as physical signals.

The BCH, the MCH, the UL-SCH, and the DL-SCH are transport channels. A channel used in the Medium Access Control (MAC) layer is referred to as a transport channel. A unit of the transport channel used in the MAC layer is also referred to as a transport block (TB) or a MAC Protocol Data Unit (PDU). A Hybrid Automatic Repeat reQuest (HARQ) is controlled for each transport block in the MAC layer. The transport block is a unit of data that the MAC layer delivers to the physical layer. In the physical layer, the transport block is mapped to a codeword, and coding processing is performed for each codeword.

A structure of a radio frame in the present embodiment will be described.

FIG. 3 is a diagram illustrating a schematic configuration of a radio frame according to the present embodiment. In FIG. 3, the horizontal axis is a time axis. Each type 1 radio frame is 10 ms in length, and is defined by 10 subframes. Each of the subframes is 1 ms in length and is defined by two consecutive slots. Each of the slots is 0.5 ms in length. The i-th subframe within a radio frame includes the (2×i)-th slot and the (2×i+1)-th slot.

The number of symbols included in one subframe described above may be defined based on a Subcarrier Spacing for a physical channel used for transmission and/or reception. For example, in a case that the subcarrier spacing is 15 kHz, the number of symbols included in one subframe may be 14. Furthermore, in a case that the subcarrier spacing is 30 kHz, the number of symbols included in one subframe may be 28. Here, the subcarrier spacing may be any of 3.75 kHz, 7.5 kHz, 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz. Obviously, a reduced subcarrier spacing increases a symbol length, and an increased subcarrier spacing reduces the symbol length. The symbol used for the uplink transmission is an OFDM (CP-OFDM, Cyclic Prefix-OFDM) symbol, or an SC-FDMA (DFT-S-OFDM) symbol. The symbol used for the downlink transmission is the OFDM symbol. Furthermore, the subframe may include one or more slots.

A transmission timing of the HARQ-ACK for the downlink transmission (PDSCH) according to the present embodiment will be described.

For the transmission timing of the HARQ-ACK for the PDSCH, in a case that the terminal apparatus 1 detects the PDSCH in a subframe n−j for FDD, the terminal apparatus 1 transmits HARQ-ACK for the PDSCH in a subframe n. That is, the transmission timing of the HARQ-ACK for the PDSCH corresponds to the j-th succeeding subframe from the subframe in which the PDSCH has been transmitted.

Hereinafter, the transmission timing of the PUSCH for the uplink grant according to the present embodiment will be described.

For a transmission timing of the PUSCH for the uplink grant, in a case that the terminal apparatus 1 detects the PDCCH (uplink grant) in the subframe n for FDD, the terminal apparatus 1 transmits the PUSCH for the uplink grant in a subframe n+k. That is, the transmission timing of the PUSCH for the uplink grant corresponds to the k-th succeeding subframe from the subframe in which the uplink grant has been detected.

For the FDD, k and j may be 4. k and j that are each 4 may be referred to as normal timings (normal processing time). With the normal processing time, the transmission timing of the HARQ-ACK for the PDSCH and the transmission timing of the PUSCH for the uplink grant each correspond to four subframes.

Furthermore, the value of k and/or j may be a value smaller than 4. For example, the value of k and/or j may be 3. Furthermore, for example, the value of k and/or j may be 2. The value of k and/or j may be determined depending on the processing capability of the terminal apparatus 1. k and j that are each smaller than 4 may be referred to as a reduced timing (reduced processing time, short processing time). With the short processing time, the transmission timing of the HARQ-ACK for the PDSCH and the transmission timing of the PUSCH for the uplink grant correspond to fewer than four subframes. That is, the shortening processing capability of the terminal apparatus 1 is the capability of transmitting and/or receiving data by using the short processing time. Here, the value of k and/or j is defined by specifications or the like, and may be a value known to the base station apparatus 3 and the terminal apparatus 1.

Here, the processing capability of the terminal apparatus 1 may be indicated by capability information about the terminal apparatus 1. In the present embodiment, shortening capability information about the terminal apparatus 1 may be capability information about the terminal apparatus 1 associated with support (or non-support) of the capability of shortening the normal processing time. The terminal apparatus 1 with the shortening processing capability can transmit and/or receive data by using a processing time (short processing time) shorter than the normal processing time.

In a case that the base station apparatus 3 (EUTRAN) needs the capability information about the terminal apparatus 1, the base station apparatus 3 initiates a procedure relating to obtaining the capability information about the terminal apparatus 1 in a connected mode (that is, the terminal apparatus 1 for which an RRC connection is established). The base station apparatus 3 queries the capability information (e.g., the shortening processing capability) about the terminal apparatus 1. The terminal apparatus 1 transmits the capability information about the terminal apparatus 1 to the base station apparatus 3 in response to the query. The base station apparatus 3 determines whether or not the terminal apparatus 1 supports a prescribed capability based on the capability information of the terminal apparatus 1. In a case that the terminal apparatus 1 supports the prescribed capability, the base station apparatus 3 transmits configuration information corresponding to the prescribed capability to the terminal apparatus 1 by using higher layer signaling or the like. Based on whether or not the configuration information corresponding to the capability information is configured, the terminal apparatus 1 determines whether to perform transmission and/or reception based on the capability or to perform transmission and/or reception not based on the capability. For example, the configuration information corresponding to the shortening processing capability may be defined as an RRC layer parameter reducedProcessingTiming. The terminal apparatus 1 configured with the RRC layer parameter reducedProcessingTiming may transmit and/or receive data by using the short processing time. Furthermore, the terminal apparatus 1 not configured with the RRC layer parameter reducedProcessingTiming may transmit and/or receive data using the normal processing time.

The RRC layer parameter reducedProcessingTiming is a parameter indicating whether or not to perform data transmission and/or reception based on the short processing time in a certain serving cell. Here, configuration of the RRC parameter reducedProcessingTiming indicates that the value of the parameter reducedProcessingTiming transmitted by the higher layer signaling is True. The parameter reducedProcessingTiming configured with a value True may also include that transmission and/or reception is performed using the short processing time (e.g., 3 ms). Hereinafter, a lack of configuration of the RRC parameter reducedProcessingTiming may indicate that the value of the parameter reducedProcessingTiming transmitted by the higher layer signaling is False or that the received higher layer signaling (higher layer information) does not include the RRC parameter reducedProcessingTiming. The parameter reducedProcessingTiming configured with a value False may also include that transmission and/or reception is performed using the normal processing time (e.g., 4 ms).

Note that the RRC parameter reducedProcessingTiming may be defined for the serving cell. That is, the base station apparatus 3 may transmit (notify), to the terminal apparatus 1, information about whether or not the RRC parameter reducedProcessingTiming is configured for each serving cell. The terminal apparatus 1 not configured with the RRC parameter reducedProcessingTiming for the certain serving cell may perform transmission and/or reception by using the normal processing time in the serving cell. The terminal apparatus 1 configured with the RRC parameter reducedProcessingTiming for a certain serving cell may perform transmission and/or reception by using the short processing time (e.g., 3 ms) in the serving cell. Here, in a case that the downlink assignment or the uplink grant in the serving cell in which the RRC parameter reducedProcessingTiming is configured is detected in a common search space, the terminal apparatus 1 may perform transmission and/or reception by using the normal processing time. Additionally, in a case that the downlink assignment or the uplink grant in the serving cell is detected in a UE-specific search space, the terminal apparatus 1 may perform transmission and/or reception by using the short processing time. Whether to configure the RRC parameter reducedProcessingTiming for a certain serving cell is optional for higher layer (RRC).

Here, the serving cell includes component carriers used for the downlink and component carriers used for the uplink. Linking may be defined between the uplink component carriers and the downlink component carriers. The RRC parameter reducedProcessingTiming may be applied to both the uplink component carriers and the downlink component carriers included in the same linking. The terminal apparatus 1 may identify the serving cell for the uplink grant (serving cell in which transmission on the PUSCH scheduled by the uplink grant (uplink transmission) is performed) based on the linking between the uplink and the downlink. Between the uplink component carrier and the downlink component carrier included in the same linking, no carrier indicator field is present in the downlink assignment or the uplink grant. Furthermore, in a case that, by the downlink assignment or the uplink grant in the serving cell configured with the RRC parameter reducedProcessingTiming, transmission and/or reception in another serving cell not configured with the RRC parameter reducedProcessingTiming is scheduled, the terminal apparatus 1 may perform transmission and/or reception using the normal processing time.

Note that the RRC parameter reducedProcessingTiming may be defined independently for the uplink component carriers and for the downlink component carriers. In other words, the RRC parameter reducedProcessingTiming may be defined for each of the downlink and the uplink. That is, the base station apparatus 3 may transmit (notify), to the terminal apparatus 1, information about whether or not the RRC parameter reducedProcessingTiming is configured for each uplink component carrier. Furthermore, the base station apparatus 3 may transmit (notify), to the terminal apparatus 1, information about whether or not the RRC parameter reducedProcessingTiming is configured for each downlink component carrier. For example, the terminal apparatus 1 configured with the RRC parameter reducedProcessingTiming for a certain uplink component carrier may transmit the PUSCH by using the short processing time (e.g., 3 ms) for the uplink component carrier. The terminal apparatus 1 not configured with the RRC parameter reducedProcessingTiming for the certain uplink component carrier may transmit the PUSCH by using the normal processing time for the uplink component carrier. Furthermore, for example, the terminal apparatus 1 configured with the RRC parameter reducedProcessingTiming for the certain downlink component carrier may transmit the HARQ-ACK for the PDSCH in the downlink component carrier by using the short processing time. The terminal apparatus 1 not configured with the RRC parameter reducedProcessingTiming for the certain downlink component carrier may transmit the HARQ-ACK for the PDSCH in the downlink component carrier by using the normal processing time.

Note that the RRC parameter reducedProcessingTiming may be defined for each of Timing Advance Groups (TAGs). The base station apparatus 3 may transmit (notify), to the terminal apparatus 1, information about whether or not the RRC parameter reducedProcessingTiming is configured for each TAG. The configuration related to the RRC parameter reducedProcessingTiming may be applied to each of the serving cells belonging to the same Timing Advance Group (TAG). For example. The terminal apparatus 1 configured with the RRC parameter reducedProcessingTiming for a certain TAG may perform transmission and/or reception by using the short processing time in a serving cell belonging to the TAG. The terminal apparatus 1 not configured with the RRC parameter reducedProcessingTiming for the certain TAG may perform transmission and/or reception by using the normal processing time in the serving cell belonging to the TAG.

Hereinafter, DCI format 0 for describing a DCI format according to the present embodiment is used for scheduling of the PUSCH. DCI Format 0 does not include the “Redundancy version” field and the “HARQ process number” field. Furthermore, DCI format OD includes the uplink grant and is used for scheduling of the PUSCH. DCI format OD includes the “Redundancy version” field and the “HARQ process number” field. Here, DCI format OD may be used for scheduling of the PUSCH in a serving cell configured with the short processing time. Note that DCI format 0 and DCI format OD may be referred to as the uplink grant.

The terminal apparatus 1 not configured with the RRC layer parameter reducedProcessingTiming for the serving cell may decode the PDCCH including DCI format 0 in the common search space and the UE-specific search space in the serving cell. The terminal apparatus 1 not configured with the RRC layer parameter reducedProcessingTiming for the serving cell may not decode the PDCCH including DCI format OD in the UE-specific search space in the serving cell. DCI format 0 may be used for an uplink synchronous HARQ. The terminal apparatus 1 configured with the RRC layer parameter reducedProcessingTiming for the serving cell may decode the PDCCH including DCI format 0 in the common search space in the serving cell and decode the PDCCH including DCI format OD in the UE-specific search space in the serving cell. The terminal apparatus 1 configured with the RRC layer parameter reducedProcessingTiming for the serving cell need not decode the PDCCH including DCI format 0 in the UE-specific search space in the serving cell. DCI format OD may be used for an uplink asynchronous HARQ. DCI format OD is not used for the uplink synchronous HARQ. The number of the uplink HARQ process is provided by the HARQ process number″ field included in DCI format OD. For FDD, the terminal apparatus 1 may transmit the PUSCH in the third succeeding subframe from the subframe in which the PDCCH has been decoded, based on decoding of the PDCCH including DCI format OD in the UE-specific search space. Furthermore, based on decoding of the PDCCH including DCI format 0 in the common search space, the terminal apparatus 1 may transmit the PUSCH in the fourth succeeding subframe from the subframe in which the PDCCH has been decoded.

The HARQ process in the uplink includes the synchronous HARQ and the asynchronous HARQ. Hereinafter, the synchronous HARQ in the uplink will be described.

In the synchronous HARQ, the HARQ process to which the uplink grant corresponds is associated with a subframe in which the uplink grant has been received and/or a subframe in which PUSCH (UL-SCH) corresponding to the uplink grant is transmitted. In the synchronous HARQ, the terminal apparatus 1 derives the HARQ process to which the uplink grant corresponds from the subframe in which the uplink grant has been received and/or the subframe in which PUSCH (UL-SCH) corresponding to the uplink grant is transmitted. That is, in the synchronous HARQ, the HARQ entity may identify the HARQ process to which the uplink grant corresponds without using the information included in the uplink grant.

FIG. 4 is a diagram illustrating an example of the uplink synchronous HARQ according to the present embodiment. In FIG. 4, one subframe corresponds to one HARQ process. In FIG. 4, numbers in rectangles indicate the numbers of corresponding HARQ processes. In the synchronous HARQ, the HARQ entity derives the HARQ process from a subframe in which UL-SCH data in the MAC layer is transmitted or a subframe in which DCI format 0 corresponding to the UL-SCH data in the MAC layer has been detected.

In FIG. 4, the subframe in which the MAC layer data corresponding to the uplink grant is transmitted is derived from the subframe in which the uplink grant has been received. For example, the UL-SCH data in the MAC layer corresponding to the uplink grant may be transmitted on the PUSCH in the fourth succeeding subframe from the subframe in which the uplink grant has been received.

In synchronous HARQ, the HARQ indicator is transmitted on the PHICH in response to an uplink transmission. The correspondence between the subframe in which the uplink transmission has been performed and the subframe in which the corresponding PHICH is transmitted is predetermined. For example, the HARQ indicator for the MAC layer data is transmitted on the PHICH in the fourth succeeding subframe from the subframe in which the MAC layer data has been transmitted on the PUSCH. Furthermore, for example, the MAC layer data is retransmitted on the PUSCH in the fourth succeeding subframe from the subframe in which the NACK has been received on the PHICH.

Hereinafter, the asynchronous HARQ in the uplink according to the present embodiment will be described.

FIG. 5 is a diagram illustrating an example of the uplink asynchronous HARQ according to the present embodiment. In FIG. 5, one subframe corresponds to one HARQ process. In FIG. 5, numbers in rectangles indicate the numbers of corresponding HARQ processes. In the asynchronous HARQ, in a case that the uplink grant is included in the PDCCH mapped to a UE-specific search space, the HARQ entity derives the HARQ process from an “HARQ process number” field. In the asynchronous HARQ, in a case that the uplink grant is included in a random access response, the HARQ entity may use HARQ process with a specific number. The specific number may be 0. The specific number may be a predetermined number.

In the asynchronous HARQ, the HARQ indicator is not transmitted on the PHICH in response to the uplink transmission. That is, in the asynchronous HARQ, retransmissions of the MAC layer data (transport block) are always scheduled via the PDCCH. In FIG. 5, the subframe in which the MAC layer data corresponding to the uplink grant is transmitted is derived from the subframe in which the uplink grant has been received. For example, with the short processing time, MAC layer data corresponding to the uplink grant may be transmitted on the PUSCH in a subframe three subframes after the subframe in which the uplink grant has been received.

In the present embodiment, whether the synchronous HARQ or the asynchronous HARQ is applied to the uplink HARQ process in a certain serving cell may be derived based on whether the RRC layer parameter reducedProcessingTiming is configured for the serving cell or not. In a serving cell not configured with the RRC layer parameter reducedProcessingTiming, the synchronous HARQ may be applied to the uplink HARQ process. In a serving cell configured with the RRC layer parameter reducedProcessingTiming, the asynchronous HARQ may be applied to the uplink HARQ process. Furthermore, whether the synchronous HARQ or the asynchronous HARQ is applied to the uplink HARQ process in the serving cell configured with the RRC layer parameter reducedProcessingTiming may be derived from the type of the search space in which the uplink grant has been received. For example, in a case that the uplink grant corresponding to the uplink HARQ process is received in the common search space, the type of uplink HARQ process may be the synchronous HARQ. In other words, the synchronous HARQ is applied to the MAC layer data corresponding to the uplink grant received in the common search space. Furthermore, in a case that the uplink grant corresponding to the uplink HARQ process is received in the UE-specific search space, the type of the uplink HARQ process may be the asynchronous HARQ. In other words, the asynchronous HARQ is applied to the MAC layer data corresponding to the uplink grant received in the UE-specific search space.

In the present embodiment, the HARQ process manages a state variable HARQ_FEEDBACK. The HARQ process indicates to the physical layer to generate a transmission in response to the uplink grant in a case that the HARQ entity requests a non-adaptive retransmission and the NACK is set in the state variable HARQ_FEEDBACK.

The HARQ process to which the synchronous HARQ is applied sets the ACK or the NACK in the state variable HARQ_FEEDBACK based on the HARQ indicator received on the PHICH. The HARQ process to which the asynchronous HARQ is applied need not set the ACK or the NACK in the state variable HARQ_FEEDBACK, based on the HARQ indicator received on the PHICH.

The HARQ process to which the synchronous HARQ is applied sets the NACK in the state variable HARQ_FEEDBACK, based on the initial transmission from the HARQ entity or a request for non-adaptive retransmission. Furthermore, the HARQ process to which the asynchronous HARQ is applied sets the ACK in the state variable HARQ_FEEDBACK, based on the initial transmission from the HARQ entity or the request for adaptive retransmission. Note that the adaptive retransmission is retransmission indicated by the NDI and non-adaptive retransmission is retransmission indicated by the HARQ indicator. This prevents the HARQ process to which the asynchronous HARQ is applied from performing the non-adaptive retransmission. Additionally, in a case that only the HARQ ACK is received, the corresponding HARQ process keeps the MAC layer data in HARQ buffer.

A procedure relating to the PHICH according to the present embodiment will be described below.

FIG. 6 is a diagram illustrating an example of PUSCH synchronous transmission by the PHICH according to the present embodiment. In FIG. 6, one subframe corresponds to one HARQ process. In FIG. 6, numbers in rectangles indicate the number of corresponding HARQ processes.

In FIG. 6, the terminal apparatus 1 transmits the PUSCH in a subframe n−4. In FIG. 6, the terminal apparatus 1 receives the PHICH in a subframe n. The PHICH in the subframe n is associated with the PUSCH transmitted in the subframe n−4. The PHICH in the subframe n is used to transmit the HARQ indicator indicating the ACK or NACK for the transport block transmitted on the PUSCH of the subframe n−4. In other words, in a case that a certain transport block is transmitted on the PUSCH in the subframe n−4, the HARQ indicator indicating the ACK or NACK for the transport block is transmitted (allocated) on the PHICH in the subframe n. Here, for example, the number of the HARQ process corresponding to the PUSCH (transport block) transmitted in the subframe n−4 corresponds to 0.

Next, the terminal apparatus 1 may determine whether or not to trigger non-adaptive retransmission of the transport block based on the HARQ indicator transmitted on the PHICH in the subframe n. For example, in a case that the ACK is decoded on the PHICH in the subframe n, the ACK for the transport block may be delivered to a higher layer. That is, the non-adaptive retransmission of the transport block corresponding to the HARQ process number 0 may not be performed in a subframe n+4. After the ACK has been decoded, retransmission or initial transmission of the transport block corresponding to the HARQ process number 0 is scheduled via the PDCCH.

Furthermore, for example, in a case that the NACK is decoded on the PHICH in the subframe n, the NACK for the transport block may be delivered to a higher layer. That is, the non-adaptive retransmission of the transport block corresponding to the HARQ process number 0 may be performed in the subframe n+4. Then, after performing transmission of the PUSCH in the subframe n+4, the terminal apparatus 1 may attempt to receive the PHICH for the PUSCH, in a subframe n+8. In addition, due to the occurrence of a measurement gap, the non-adaptive retransmission of the transport block on the PUSCH in the subframe n+4 is not performed in some cases. For example, in a case that the subframe n+4 in which the non-adaptive retransmission of the transport block corresponding to the HARQ process number 0 is attempted to be performed is a part of the measurement gap configured to a higher layer, the terminal apparatus 1 does not perform the non-adaptive retransmission of the transport block in the subframe n+4. Subsequently, the terminal apparatus 1 may not attempt to receive the PHICH in the subframe n+8, and may continuously perform the non-adaptive retransmission of the transport block corresponding to the HARQ process number 0 in a subframe n+12.

The measurement gap is a time interval for the terminal apparatus 1 to perform measurements of cells operating on different frequencies and/or operating in different Radio Access Technologies (RATs). The base station apparatus 3 transmits information indicating the period of the measurement gap to the terminal apparatus 1. The terminal apparatus 1 configures the period of the measurement gap, based on the information. The terminal apparatus 1 need not perform uplink transmission in a subframe that is a part of the measurement gap.

FIG. 7 is a diagram illustrating an example of a collision of the PUSCH transmission due to different processing time according to the present embodiment. Hereinafter, in FIG. 7, the terminal apparatus 1 is a terminal apparatus with the shortening processing capability, and the RRC parameter reducedProcessingTiming is configured for the serving cell, unless otherwise specified. In FIG. 7, numbers in rectangles indicate the numbers of corresponding HARQ processes. One subframe corresponds to one HARQ process. In FIG. 7, the type of the uplink HARQ process may be determined based on the type of the search space in which the uplink grant is transmitted. For example, in a case that the uplink grant is received in the UE-specific search space, the asynchronous HARQ may be applied to the HARQ process corresponding to the PUSCH scheduled by the uplink grant. The terminal apparatus 1 may perform transmission of the PUSCH in a third succeeding subframe from the subframe in which the uplink grant has been received. The HARQ entity derives the number of the HARQ process from the “HARQ process number” field included in the uplink grant. Furthermore, in a case that the uplink grant is received in the common search space, the synchronous HARQ may be applied to the HARQ process corresponding to the PUSCH scheduled by the uplink grant. The terminal apparatus 1 may perform transmission of the PUSCH in a fourth succeeding subframe from the subframe in which the uplink grant has been received. The HARQ entity may derive the number of the HARQ process based at least on the subframe number at which the PUSCH is transmitted.

In FIG. 7, in the subframe n−4, the terminal apparatus 1 transmits the transport block corresponding to the HARQ process to which the synchronous HARQ is applied, on the PUSCH. In the HARQ process to which the uplink synchronous HARQ is applied, the HARQ indicator is transmitted on the PHICH in response to transmission of the transport block. Furthermore, the correspondence between the subframe in which the PHICH including the HARQ indicator is transmitted in response to the transmission of the transport block and the subframe in which the transport block has been transmitted is predetermined. The terminal apparatus 1 attempts to receive the PHICH including the HARQ indicator for the transmission of the transport block in the fourth succeeding subframe from the subframe in which the transport block has been transmitted on the PUSCH. Similarly, the terminal apparatus 1 may perform the non-adaptive retransmission of the transport block in a fourth succeeding subframe from the subframe in which the HARQ indicator indicating the NACK has been received on PHICH. In FIG. 7, the terminal apparatus 1 may attempt to receive the HARQ indicator for the transport block transmitted on the PUSCH of the subframe n−4, on the PHICH in the subframe n. In a case that the HARQ indicator indicating the NACK is received on the PHICH in the subframe n, the terminal apparatus 1 performs the non-adaptive retransmission of the transport block in the subframe n+4. Here, in FIG. 7, the number of the HARQ process, to which the synchronous HARQ is applied, corresponding to the transport block transmitted on the PUSCH in the subframe n−4 corresponds to 0. Additionally, in a case that the uplink grant indicating the same HARQ process (HARQ process number 0) is detected in subframes from the subframe n to the subframe n+3, the terminal apparatus 1 may stop the non-adaptive retransmission of the transport block corresponding to the HARQ process number 0, and may perform any one of the initial transmission or the adaptive retransmission of the transport block corresponding to the HARQ process number 0 based on the detected uplink grant.

Next, in a subframe n+1, in a case that the uplink grant is detected in the UE-specific search space, the terminal apparatus 1 may perform transmission of the transport block scheduled by the uplink grant on the PUSCH of the subframe n+4. As described above, in a case that the uplink grant for scheduling the transmission of the transport block is detected in the UE-specific search space, the transmission timing of the transport block may be configured to 3 ms (three subframes). In addition, the asynchronous HARQ may be applied to the HARQ process corresponding to the transport block. The number of the HARQ process corresponding to the transport block is provided based on the “HARQ process number” field included in the uplink grant. For example, in FIG. 7, the transmission of the transport block scheduled by the uplink grant corresponds to the HARQ process number 1. In other words, in FIG. 7, the transmission of the transport block requested by the HARQ indicator indicating the NACK and the transmission of the transport block scheduled by the uplink grant correspond to different HARQ processes.

As illustrated in FIG. 7, the transmission of the transport block requested by the HARQ indicator indicating the NACK and the transmission of the transport block scheduled by the uplink grant occur in the same subframe. However, there is a possibility that the terminal apparatus 1 cannot perform simultaneous transmission in the same subframe. Hereinafter, in the present embodiment, in a case that an uplink transmission collision occurs as illustrated in FIG. 7, an example in which the uplink transmission is efficiently performed will be described.

Hereinafter, the transmission of the transport block corresponding to a first HARQ process is non-adaptive retransmission requested by the HARQ indicator indicating NACK, and may be performed on the PUSCH of the fourth succeeding uplink subframe from the subframe in which the PHICH including the HARQ indicator has been received. The transmission of the transport block corresponding to a second HARQ process may be scheduled by the uplink grant in the UE-specific search space, and may be performed in the third succeeding uplink subframe from the subframe in which the uplink grant has been received. Note that the first HARQ process and the second HARQ process may correspond to different numbers of the HARQ processes.

In one aspect of the present embodiment, the terminal apparatus 1 may determine whether or not to attempt to receive the PHICH in the subframe n+8 based at least on an event in which the transmission of the transport block corresponding to the first HARQ process is stopped (not transmitted) in the subframe n+4. Here, the event in which the transmission of the transport block corresponding to the first HARQ process is stopped (not transmitted) in the subframe n+4 may include an event (i) occurrence of the measurement gap in the subframe n+4, and an event (ii) occurrence of the transmission of the transport block corresponding to the second HARQ process in the same subframe (subframe n+4). Note that the second HARQ process is a different HARQ process from the first HARQ process.

For example, in a case that the transmission of the transport block corresponding to the first HARQ process is stopped (no transmission) in the subframe n+4 by the event (i) occurrence of the measurement gap, the terminal apparatus 1 may perform transmission of the transport block corresponding to the first HARQ process in the subframe n+12 without attempting to receive the PHICH in the subframe n+8. In addition, in a case that the transmission of the transport block corresponding to the first HARQ process overlaps with the measurement gap configured in the higher layer, the terminal apparatus 1 may perform transmission of the transport block corresponding to the first HARQ process in the subframe n+12 without attempting to receive the PHICH in the subframe n+8.

Furthermore, for example, in a case that the transmission of the transport block corresponding to the first HARQ process is stopped (no transmission) by the event (ii) occurrence of the transmission of the transport block scheduled by the uplink grant in the same subframe (subframe n+4), the terminal apparatus 1 may attempt to receive the PHICH in the subframe n+8. The terminal apparatus 1 may determine whether or not to perform the transmission of the transport block corresponding to the first HARQ process based on the HARQ indicator included in the received PHICH.

In other words, in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in the same subframe, the terminal apparatus 1 may perform the transmission of the transport block corresponding to the second HARQ process on the PUSCH of the subframe, may stop the transmission of the transport block corresponding to the first HARQ process using the PUSCH of the subframe, and may attempt to receive the PHICH in a fourth succeeding subframe from the subframe. The terminal apparatus 1 may determine whether or not to perform the transmission of the transport block corresponding to the first HARQ process based at least on the HARQ indicator included in the PHICH. Note that in FIG. 7, the first HARQ process corresponds to the HARQ process number 0. The second HARQ process corresponds to the HARQ process number 1. The terminal apparatus 1 may perform the transmission of the transport blocks corresponding to the HARQ process of the number 1 scheduled by the uplink grant in the subframe n+4, and may stop the non-adaptive retransmission of the transport block corresponding to the HARQ process of the number 0 requested by the NACK. Next, the terminal apparatus 1 may attempt to receive the PHICH including the HARQ indicator in response to the transmission of the transport block corresponding to the HARQ process of the number 0 in the subframe n+8. The PHICH in the subframe n+8 may be used to transmit the HARQ indicator indicating the ACK or NACK for the transmission of the transport block corresponding to the HARQ process of the number 0 on the PUSCH in the subframe n−4.

In addition, in a case that the ACK is decoded on the PHICH in the subframe n+8, the non-adaptive retransmission of the transport block corresponding to the HARQ process of the number 0 may not be performed in the subframe n+12. The ACK for the transport block corresponding to the HARQ process of the number 0 may be delivered to the higher layer. The retransmission or initial transmission of the transport block corresponding to the HARQ process of the number 0 is scheduled via the PDCCH. In addition, in a case that the NACK is decoded on the PHICH in the subframe n+8, the non-adaptive retransmission of the transport block corresponding to the HARQ process of the number 0 may be performed in the subframe n+12. This makes it possible to efficiently perform the transmission of the transport blocks corresponding to the HARQ processes respectively having two different numbers.

In addition, as an example, in FIG. 7, in a case that the transmission of the transport block scheduled by the uplink grant and the non-adaptive retransmission of the transport block requested by the NACK occur in the same subframe n+4, the terminal apparatus 1 may, in the subframe n+4, perform the transmission of the transport block scheduled by the uplink grant and stop the non-adaptive retransmission of the transport block corresponding to the HARQ process of the number 0 requested by the NACK, may not attempt to receive the PHICH in the subframe n+8, or may perform the non-adaptive retransmission of the transport block corresponding to the HARQ process of the number 0 in the subframe n+12.

In another aspect of the present embodiment, the terminal apparatus 1 may determine whether or not to set the state variable HARQ_FEEDBACK of the first HARQ process to the ACK based at least on an event in which the transmission of the transport block corresponding to the first HARQ process is stopped (not transmitted) in the subframe n+4.

For example, in a case that the transmission of the transport block corresponding to the first HARQ process is stopped (no transmission) in the subframe n+4 by (i) occurrence of the measurement gap, the terminal apparatus 1 may not set the state variable HARQ_FEEDBACK of the first HARQ process to the ACK. Additionally, in a case that the transmission of the transport block corresponding to the first HARQ process is stopped (no transmission) in the subframe n+4 by (i) occurrence of the measurement gap, the terminal apparatus 1 may perform the transmission (non-adaptive retransmission) of transport block corresponding to the first HARQ process in the subframe n+12.

Furthermore, for example, in a case that the transmission of the transport block corresponding to the first HARQ process is stopped (no transmission) by (ii) occurrence of the transmission of the transport block scheduled by the uplink grant in the same subframe (subframe n+4), the terminal apparatus 1 may set the state variable HARQ_FEEDBACK of the first HARQ process to the ACK. The initial transmission or the adaptive retransmission of the transport block corresponding to the first HARQ process is scheduled via the PDCCH. Here, the PDCCH includes the uplink grant mapped to the common search space and/or the UE-specific search space.

Here, in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in the same subframe, the terminal apparatus 1 may set the state variable HARQ_FEEDBACK of the first HARQ process to the ACK, may stop the non-adaptive retransmission of the transport block corresponding to the first HARQ process on the PUSCH of the subframe, and may perform the transmission of the transport block corresponding to the second HARQ process on the PUSCH of the subframe. Here, the ACK for the transport block corresponding to the first HARQ process may be delivered to the higher layer. In this case, the terminal apparatus 1 may not attempt to receive the PHICH in the subframe n+8, and may not perform the transmission of the transport block corresponding to the first HARQ process in the subframe n+12.

In other words, in FIG. 7, in a case that the NACK is decoded on the PHICH in the subframe n, the terminal apparatus 1 sets NACK to the state variable HARQ_FEEDBACK of the first HARQ process of the number 0. The terminal apparatus 1 attempts to perform the non-adaptive retransmission of the transport block corresponding to the first HARQ process requested by the NACK in the subframe n+4 using the normal processing time. At this time, in a case that the terminal apparatus 1 detects, in the subframe n+1, the uplink grant corresponding to the second HARQ process of the number 1 in the UE-specific search space, the terminal apparatus 1 performs, in some cases, transmission of the transport block scheduled by the uplink grant received in the UE-specific search space in the subframe n+4 using the short processing time. In such a case, the transmission of the transport block corresponding to the first HARQ process of the number 0 and the transmission of the transport block corresponding to the second HARQ process of the number 1 may occur in the same subframe n+4. In this case, the terminal apparatus 1 may set the state variable HARQ_FEEDBACK of the first HARQ process of the number 0 to the ACK. The initial transmission or the adaptive retransmission of the transport block corresponding to the first HARQ process of the number 0 is scheduled (indicated) via the PDCCH. That is, the non-adaptive retransmission of the transport block corresponding to the first HARQ process of the number 0 may not be performed in the subframes n+4 and n+12. This makes it possible to efficiently perform the transmission of the transport blocks corresponding to the HARQ processes respectively having two different numbers.

Hereinafter, an sTTI according to the present embodiment will be described.

FIG. 8 is a diagram illustrating an example of a TTI and an sTTI according to the present embodiment. The TTI may include 2×N^(UL) _(symb) SC-FDMA symbols. Note that N^(UL) _(symb) may be the number of SC-FDMA symbols constituting one slot. In FIG. 8, the number X of SC-FDMA symbols constituting the sTTI (shortened TTI) is any one of {2, 3, 4, 7}. The TTI/sTTI including X SC-FDMA symbols is also referred to as an X-symbol TTI. In the uplink, an sPUSCH may be a channel used at least for transmission of the uplink data. An sPUCCH may be a channel used at least for transmission of the uplink control information. A TTI length of the sPUSCH and/or sPUCCH may be shorter than 1 ms (one subframe length) or 0.5 ms (one slot length). In a 2-symbol TTI, the sPUSCH and/or sPUCCH may be mapped to two SC-FDMA symbols or three SC-FDMA symbols. In a 7-symbol TTI, the sPUSCH and/or sPUCCH may be mapped to seven SC-FDMA symbols.

In the TTI, the transmission timing of the PUSCH for the uplink grant corresponds to the k-th succeeding subframe from the subframe in which the uplink grant has been detected. The value of k may be 3 and/or 4. Additionally, in the sTTI, the transmission timing of the sPUSCH for the uplink grant corresponds to an m-th succeeding sTTI from the sTTI in which the uplink grant has been detected. For example, in the 7-symbol TTI, the value of m may be 4. In other words, in the 7-symbol TTI, in a case that the uplink grant for scheduling the sPUSCH is received at a first sTTI in the subframe n, the transmission of the sPUSCH may be performed at the first sTTI in the subframe n+2. For example, in the 2-symbol TTI, the value of m may be 6. In other words, in the 2-symbol TTI, in a case that the uplink grant for scheduling the sPUSCH is received at the first sTTI in the subframe n, the transmission of the sPUSCH may be performed at the first sTTI in the subframe n+1. Furthermore, for example, in the 2-symbol TTI, the value of m may be 4. That is, the processing time of the sPUSCH is shorter than the processing time of the PUSCH.

Hereinafter, in the present embodiment, a case in which the transmission of the transport block corresponding to the first HARQ process and the transmission of the sPUSCH occur in the same subframe will be described. Here, the transport block transmitted on the sPUSCH corresponds to a third HARQ process. That is, the transport block transmitted on the sPUSCH may be a different HARQ process from the first HARQ process. Note that the first HARQ process and the third HARQ process correspond to different HARQ process numbers. Here, the transmission of the transport block corresponding to the first HARQ process may be paraphrased as the transmission of the PUSCH corresponding to the first HARQ process. Since the processing time from the detection of the uplink grant to the transmission of the sPUSCH is shorter than the processing time for the PUSCH, even in case that the uplink grant for scheduling the transmission of the sPUSCH is received at a later timing than that of the uplink grant for scheduling the transmission of the PUSCH, the sPUSCH is transmitted, in some cases, in the same subframe as the PUSCH.

In such a case, the transmission of the transport block corresponding to the first HARQ process may be, by an event (iii) occurrence of the transmission of the sPUSCH corresponding to the third HARQ process in the same subframe, stopped (may not be performed) in the subframe. In the present embodiment, an operation after the transmission of the transport block corresponding to the first HARQ process has been stopped by the event (iii) occurrence of the transmission of the sPUSCH corresponding to the third HARQ process in the same subframe may be the same as an operation after the transmission of the transport block corresponding to the first HARQ process has been stopped by the event (ii) occurrence of the transmission of the transport block corresponding to the second HARQ process in the same subframe. Whether or not to perform the operation as described above may be determined based on the capability information of the terminal apparatus 1. In other words, in the present embodiment, in a case that the transmission of the transport block corresponding to the first HARQ process is stopped due to a certain condition, the operation of the terminal apparatus 1 after the stop may be common (the same).

Additionally, the transmission of the transport block corresponding to the first HARQ process being stopped by the event (iii) occurrence of the transmission of the sPUSCH corresponding to the third HARQ process in the same subframe may at least include that (A) the transport block corresponding to the first HARQ process is not transmitted by all symbols of the PUSCH and/or (B) the transport block corresponding to the first HARQ process is not transmitted by part of the symbols of the PUSCH. In addition, in (B), the transport block corresponding to the first HARQ process may not be transmitted by a symbol overlapping with the sPUSCH. In addition, in (B), the transport block corresponding to the first HARQ process may not be transmitted by a slot overlapping with the sPUSCH.

Configurations of apparatuses according to the present embodiment will be described below.

FIG. 9 is a schematic block diagram illustrating a configuration of the terminal apparatus 1 according to the present embodiment. As illustrated, the terminal apparatus 1 is configured to include a radio transmission and/or reception unit 10 and a higher layer processing unit 14. The radio transmission and/or reception unit 10 is configured to include an antenna unit 11, a Radio Frequency (RF) unit 12, and a baseband unit 13. The higher layer processing unit 14 is configured to include a medium access control layer processing unit 15 and a radio resource control layer processing unit 16. The radio transmission and/or reception unit 10 is also referred to as a transmission unit, a reception unit or a physical layer processing unit.

The higher layer processing unit 14 outputs uplink data (transport block) generated by a user operation or the like, to the radio transmission and/or reception unit 10. The higher layer processing unit 14 performs processing of the Medium Access Control (MAC) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and the Radio Resource Control (RRC) layer.

The medium access control layer processing unit 15 included in the higher layer processing unit 14 performs processing of the Medium Access Control layer. The medium access control layer processing unit 15 controls HARQ in accordance with the various pieces of configuration information/parameters managed by the radio resource control layer processing unit 16. The medium access control layer processing unit 15 manages multiple HARQ entities, multiple HARQ processes, and multiple HARQ buffers.

The medium access control layer processing unit 15 indicates the radio transmission and/or reception unit 10 to monitor the PDCCH and/or PHICH in the subframe. The monitoring of the PDCCH denotes an attempt to decode the PDCCH in accordance with a DCI format. The monitoring of the PHICH denotes an attempt to receive the PHICH including the HARQ indicator for transmission of a certain transport block. The HARQ process managed by the medium access control layer processing unit 15 sets the ACK or the NACK in the state variable HARQ_FEEDBACK based on the HARQ indicator.

The radio resource control layer processing unit 16 included in the higher layer processing unit 14 performs processing of the Radio Resource Control layer. The radio resource control layer processing unit 16 manages various types of configuration information/parameters of its own apparatus. The radio resource control layer processing unit 16 sets the various pieces of configuration information/parameters in accordance with RRC layer signaling received from the base station apparatus 3. Namely, the radio resource control layer processing unit 16 sets the various configuration information/parameters in accordance with the information indicating the various configuration information/parameters received from the base station apparatus 3.

The radio transmission and/or reception unit 10 performs processing of the physical layer, such as modulation, demodulation, coding, decoding, and the like. The radio transmission and/or reception unit 10 demultiplexes, demodulates, and decodes a signal received from the base station apparatus 3, and outputs the information resulting from the decoding to the higher layer processing unit 14. The radio transmission and/or reception unit 10 generates a transmit signal by modulating and coding data, and performs transmission to the base station apparatus 3.

The RF unit 12 converts (down-converts) a signal received via the antenna unit 11 into a baseband signal by orthogonal demodulation and removes unnecessary frequency components. The RF unit 12 outputs the processed analog signal to the baseband unit.

The baseband unit 13 converts the analog signal input from the RF unit 12 into a digital signal. The baseband unit 13 removes a portion corresponding to a Cyclic Prefix (CP) from the digital signal resulting from the conversion, performs Fast Fourier Transform (FFT) of the signal from which the CP has been removed, and extracts a signal in the frequency domain.

The baseband unit 13 generates an SC-FDMA symbol by performing Inverse Fast Fourier Transform (IFFT) of the data, adds CP to the generated SC-FDMA symbol, generates a baseband digital signal, and converts the baseband digital signal into an analog signal. The baseband unit 13 outputs the analog signal resulting from the conversion, to the RF unit 12.

The RF unit 12 removes unnecessary frequency components from the analog signal input from the baseband unit 13 using a low-pass filter, up-converts the analog signal into a signal of a carrier frequency, and transmits the up-converted signal via the antenna unit 11. Furthermore, the RF unit 12 amplifies power. Furthermore, the RF unit 12 may have a function of controlling transmit power. The RF unit 12 is also referred to as a transmit power control unit.

FIG. 10 is a schematic block diagram illustrating a configuration of the base station apparatus 3 according to the present embodiment. As illustrated, the base station apparatus 3 is configured to include a radio transmission and/or reception unit 30 and a higher layer processing unit 34. The radio transmission and/or reception unit 30 is configured to include an antenna unit 31, an RF unit 32, and a baseband unit 33. The higher layer processing unit 34 is configured to include a medium access control layer processing unit 35 and a radio resource control layer processing unit 36. The radio transmission and/or reception unit 30 is also referred to as a transmission unit, a reception unit or a physical layer processing unit.

The higher layer processing unit 34 performs processing of the Medium Access Control (MAC) layer, the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, and the Radio Resource Control (RRC) layer.

The medium access control layer processing unit 35 included in the higher layer processing unit 34 performs processing of the Medium Access Control layer. The medium access control layer processing unit 15 controls HARQ in accordance with the various pieces of configuration information/parameters managed by the radio resource control layer processing unit 16. The medium access control layer processing unit 15 generates an ACK/NACK and HARQ information with respect to uplink data (UL-SCH). The ACK/NACK and HARQ information with respect to the uplink data (UL-SCH) are transmitted to the terminal apparatus 1 on the PHICH or the PDCCH.

The radio resource control layer processing unit 36 included in the higher layer processing unit 34 performs processing of the Radio Resource Control layer. The radio resource control layer processing unit 36 generates, or acquires from a higher node, downlink data (transport block) allocated on a physical downlink shared channel, system information, an RRC message, a MAC Control Element (CE), and the like, and performs output to the radio transmission and/or reception unit 30. Furthermore, the radio resource control layer processing unit 36 manages various types of configuration information/parameters for each of the terminal apparatuses 1. The radio resource control layer processing unit 36 may set various types of configuration information/parameters for each of the terminal apparatuses 1 via the higher layer signal. That is, the radio resource control layer processing unit 36 transmits/broadcasts information indicating various types of configuration information/parameters.

The functionality of the radio transmission and/or reception unit 30 is similar to the functionality of the radio transmission and/or reception unit 10, and hence description thereof is omitted.

Each of the units having the reference signs 30 to 36 included in the base station apparatus 3 may be configured as a circuit. Each of the units having the reference signs 10 to 16 included in the terminal apparatus 1 may be configured as a circuit.

Hereinafter, various aspects of the terminal apparatus and the base station apparatus in the present embodiment will be described.

(1) A first aspect of the present embodiment is a terminal apparatus, the terminal apparatus including: a reception unit 10 configured to receive a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and a transmission unit 10 configured to perform, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission, on the PUSCH, of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission, on the PUSCH, of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process.

(2) In the first aspect of the present embodiment, initial transmission or adaptive retransmission of the transport block corresponding to the first HARQ process may be scheduled by using the PDCCH, and the PDCCH may be mapped to a common search space and/or a UE-specific search space.

(3) A second aspect of the present embodiment is a base station apparatus for communicating with a terminal apparatus, the base station apparatus including: a transmission unit 30 configured to transmit a PHICH including an HARQ indicator for indicating an ACK and/or an NACK and a PDCCH including an uplink grant; and a reception unit 30 configured to receive, on a PUSCH, transmission of a transport block corresponding to a first HARQ process and/or transmission of a transport block corresponding to a second HARQ process, in which the transmission, on the PUSCH, of the transport block corresponding to the first HARQ process is non-adaptive retransmission requested by the HARQ indicator for indicating the NACK and is performed on the PUSCH of a fourth succeeding uplink subframe from a subframe in which the PHICH including the HARQ indicator is received, the transmission, on the PUSCH, of the transport block corresponding to the second HARQ process is scheduled by an uplink grant and is performed on the PUSCH of a third succeeding uplink subframe from a subframe in which the uplink grant is received, and in a case that the transmission of the transport block corresponding to the first HARQ process and the transmission of the transport block corresponding to the second HARQ process occur in an identical uplink subframe, the ACK is set as a state variable HARQ_FEEDBACK of the first HARQ process by the terminal apparatus.

(4) In the second aspect of the present embodiment, initial transmission or adaptive retransmission of the transport block corresponding to the first HARQ process may be scheduled by using the PDCCH, and the PDCCH may be mapped to a common search space and/or a UE-specific search space.

With this configuration, the terminal apparatus 1 is capable of efficiently communicating with the base station apparatus 3.

A program running on the base station apparatus 3 and the terminal apparatus 1 according to an aspect of the present invention may be a program that controls a Central Processing Unit (CPU) and the like, such that the program causes a computer to operate in such a manner as to realize the functions of the above-described embodiment according to an aspect of the present invention. The information handled in these devices is temporarily stored in a Random Access Memory (RAM) while being processed. Thereafter, the information is stored in various types of Read Only Memory (ROM) such as a Flash ROM and a Hard Disk Drive (HDD), and when necessary, is read by the CPU to be modified or rewritten.

Note that the terminal apparatus 1 and the base station apparatus 3 according to the above-described embodiment may be partially achieved by a computer. In that case, this configuration may be realized by recording a program for realizing such control functions on a computer-readable recording medium and causing a computer system to read the program recorded on the recording medium for execution.

Note that it is assumed that the “computer system” mentioned here refers to a computer system built into the terminal apparatus 1 or the base station apparatus 3, and the computer system includes an OS and hardware components such as a peripheral apparatus. Furthermore, the “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and the like, and a storage apparatus such as a hard disk built into the computer system.

Moreover, the “computer-readable recording medium” may include a medium that dynamically retains a program for a short period of time, such as a communication line that is used to transmit the program over a network such as the Internet or over a communication line such as a telephone line, and may also include a medium that retains a program for a fixed period of time, such as a volatile memory within the computer system for functioning as a server or a client in such a case. Furthermore, the program may be configured to realize some of the functions described above, and also may be configured to be capable of realizing the functions described above in combination with a program already recorded in the computer system.

Furthermore, the base station apparatus 3 according to the above-described embodiment may be achieved as an aggregation (apparatus group) constituted of multiple apparatuses. Each of the apparatuses configuring such an apparatus group may include some or all portions of each function or each functional block of the base station apparatus 3 according to the above-described embodiment. The apparatus group may include each general function or each functional block of the base station apparatus 3. Furthermore, the terminal apparatus 1 according to the above-described embodiment can also communicate with the base station apparatus as the aggregation.

Furthermore, the base station apparatus 3 according to the above-described embodiment may serve as an Evolved Universal Terrestrial Radio Access Network (EUTRAN). Furthermore, the base station apparatus 3 according to the above-described embodiment may have some or all portions of the functions of a node higher than an eNodeB.

Furthermore, some or all portions of each of the terminal apparatus 1 and the base station apparatus 3 according to the above-described embodiment may be typically achieved as an LSI which is an integrated circuit or may be achieved as a chip set. The functional blocks of each of the terminal apparatus 1 and the base station apparatus 3 may be individually achieved as a chip, or some or all of the functional blocks may be integrated into a chip. Furthermore, a circuit integration technique is not limited to the LSI, and may be realized with a dedicated circuit or a general-purpose processor. Furthermore, in a case where with advances in semiconductor technology, a circuit integration technology with which an LSI is replaced appears, it is also possible to use an integrated circuit based on the technology.

Furthermore, according to the above-described embodiment, the terminal apparatus has been described as an example of a communication apparatus, but the present invention is not limited to such a terminal apparatus, and is applicable to a terminal apparatus or a communication apparatus of a fixed-type or a stationary-type electronic apparatus installed indoors or outdoors, for example, such as an Audio-Video (AV) apparatus, a kitchen apparatus, a cleaning or washing machine, an air-conditioning apparatus, office equipment, a vending machine, and other household apparatuses.

The embodiments of the present invention have been described in detail above referring to the drawings, but the specific configuration is not limited to the embodiments and includes, for example, an amendment to a design that falls within the scope that does not depart from the gist of the present invention. Furthermore, various modifications are possible within the scope of one aspect of the present invention defined by claims, and embodiments that are made by suitably combining technical means disclosed according to the different embodiments are also included in the technical scope of the present invention. Furthermore, a configuration in which constituent elements, described in the respective embodiments and having mutually the same effects, are substituted for one another is also included in the technical scope of the present invention.

INDUSTRIAL APPLICABILITY

An aspect of the present invention can be utilized, for example, in a communication system, communication equipment (for example, a cellular phone apparatus, a base station apparatus, a wireless LAN apparatus, or a sensor device), an integrated circuit (for example, a communication chip), or a program.

REFERENCE SIGNS LIST

-   1 (1A, 1B, 1C) Terminal apparatus -   3 Base station apparatus -   10 Radio transmission and/or reception unit -   11 Antenna unit -   12 RF unit -   13 Baseband unit -   14 Higher layer processing unit -   15 Medium access control layer processing unit -   16 Radio resource control layer processing unit -   30 Radio transmission and/or reception unit -   31 Antenna unit -   32 RF unit -   33 Baseband unit -   34 Higher layer processing unit -   35 Medium access control layer processing unit -   36 Radio resource control layer processing unit 

The invention claimed is:
 1. A terminal apparatus comprising: reception circuitry configured to receive a Physical Hybrid automatic repeat request Indicator Channel (PHICH) including a hybrid automatic repeat request (HARQ) indicator for indicating an ACK or an NACK and a physical downlink control channel (PDCCH) including an uplink grant; and transmission circuitry configured to transmit, on a Physical Uplink Shared Channel (PUSCH), at least one of a first transport block corresponding to a first HARQ process and a second transport block corresponding to a second HARQ process, wherein: in a case that the HARQ indicator included in the received PHICH indicates the NACK, a non-adaptive retransmission of the first transport block corresponding to the first HARQ process is performed in a 4th subframe after a subframe in which the HARQ indicator is received, in a case that a transmission of the second transport block corresponding to the second HARQ process is scheduled by the uplink grant, the transmission of the second transport block is performed in a 3rd subframe after a subframe in which the uplink grant is received, and in a case that a transmission of the first transport block corresponding to the first HARQ process collides with the transmission of the second transport block corresponding to the second HARQ process, a state variable HARQ_FEEDBACK of the first HARQ process is set to the ACK.
 2. The terminal apparatus according to claim 1, wherein the uplink grant is received in a UE-specific search space.
 3. A base station apparatus for communicating with a terminal apparatus, the base station apparatus comprising: transmission circuitry configured to transmit a Physical Hybrid automatic repeat request Indicator Channel (PHICH) including a hybrid automatic repeat request (HARQ) indicator for indicating an ACK or an NACK and a physical downlink control channel (PDCCH) including an uplink grant; and reception circuitry configured to receive, on a Physical Uplink Shared Channel (PUSCH), at least one of a first transport block corresponding to a first HARQ process and a second transport block corresponding to a second HARQ process, wherein: in a case that the HARQ indicator included in the transmitted PHICH indicates the NACK, a non-adaptive retransmission of the first transport block corresponding to the first HARQ process is performed by the terminal device in a 4th subframe after a subframe in which the HARQ indicator is transmitted, in a case that a transmission of the second transport block corresponding to the second HARQ process is scheduled by the uplink grant, the transmission of the second transport block is performed by the terminal device in a 3rd subframe after a subframe in which the uplink grant is transmitted, and in a case that a transmission of the first transport block corresponding to the first HARQ process collides with the transmission of the second transport block corresponding to the second HARQ process, the reception circuitry is further configured not to expect any further retransmissions of the first transport block corresponding to the first HARQ process.
 4. The base station apparatus according to claim 3, wherein the uplink grant is transmitted in a UE-specific search space.
 5. A communication method used for a terminal apparatus, the communication method comprising: receiving a Physical Hybrid automatic repeat request Indicator Channel (PHICH) including a hybrid automatic repeat request (HARQ) indicator for indicating an ACK or an NACK and a physical downlink control channel (PDCCH) including an uplink grant; and transmitting, on a Physical Uplink Shared Channel (PUSCH), at least one of a first transport block corresponding to a first HARQ process and a second transport block corresponding to a second HARQ process, wherein: in a case that the HARQ indicator included in the received PHICH indicates the NACK, a non-adaptive retransmission of the first transport block corresponding to the first HARQ process is performed in a 4th subframe after a subframe in which the HARQ indicator is received, in a case that a transmission of the second transport block corresponding to the second HARQ process is scheduled by the uplink grant, the transmission of the second transport block is performed in a 3rd subframe after a subframe in which the uplink grant is received, and in a case that a transmission of the first transport block corresponding to the first HARQ process collides with the transmission of the second transport block corresponding to the second HARQ process, a state variable HARQ_FEEDBACK of the first HARQ process is set to the ACK.
 6. The communication method according to claim 5, wherein the uplink grant is received in a UE-specific search space.
 7. A communication method used for a base station apparatus for communicating with a terminal apparatus, the communication method comprising: transmitting a Physical Hybrid automatic repeat request Indicator Channel (PHICH) including a hybrid automatic repeat request (HARQ) indicator for indicating an ACK or an NACK and a physical downlink control channel (PDCCH) including an uplink grant; and receiving, on a Physical Uplink Shared Channel (PUSCH), at least one of a first transport block corresponding to a first HARQ process and a second transport block corresponding to a second HARQ process, wherein: in a case that the HARQ indicator included in the transmitted PHICH indicates the NACK, a non-adaptive retransmission of the first transport block corresponding to the first HARQ process is performed by the terminal device in a 4th subframe after a subframe in which the HARQ indicator is transmitted, in a case that a transmission of the second transport block corresponding to the second HARQ process is scheduled by the uplink grant, the transmission of the second transport block is performed by the terminal device in a 3rd subframe after a subframe in which the uplink grant is transmitted, and in a case that a transmission of the first transport block corresponding to the first HARQ process collides with the transmission of the second transport block corresponding to the second HARQ process, not expecting to receive any further retransmissions of the first transport block corresponding to the first HARQ process.
 8. The communication method according to claim 7, wherein the uplink grant is transmitted in a UE-specific search space.
 9. An integrated circuit mounted in a terminal apparatus, the integrated circuit comprising: reception circuitry configured to receive a Physical Hybrid automatic repeat request Indicator Channel (PHICH) including a hybrid automatic repeat request (HARQ) indicator for indicating an ACK or an NACK and a physical downlink control channel (PDCCH) including an uplink grant; and transmission circuitry configured to transmit, on a Physical Uplink Shared Channel (PUSCH), at least one of a first transport block corresponding to a first HARQ process and a second transport block corresponding to a second HARQ process, wherein: in a case that the HARQ indicator included in the received PHICH indicates the NACK, a non-adaptive retransmission of the first transport block corresponding to the first HARQ process is performed in a 4th subframe after a subframe in which the HARQ indicator is received, in a case that a transmission of the second transport block corresponding to the second HARQ process is scheduled by the uplink grant, the transmission of the second transport block is performed in a 3rd subframe after a subframe in which the uplink grant is received, and in a case that a transmission of the first transport block corresponding to the first HARQ process collides with the transmission of the second transport block corresponding to the second HARQ process, a state variable HARQ_FEEDBACK of the first HARQ process is set to the ACK.
 10. The integrated circuit according to claim 9, wherein the uplink grant is received in a UE-specific search space.
 11. An integrated circuit mounted in a base station apparatus for communicating with a terminal apparatus, the integrated circuit causing the base station apparatus to perform: transmitting a Physical Hybrid automatic repeat request Indicator Channel (PHICH) including a hybrid automatic repeat request (HARQ) indicator for indicating an ACK or an NACK and a physical downlink control channel (PDCCH) including an uplink grant; and receiving, on a Physical Uplink Shared Channel (PUSCH), at least one of a first transport block corresponding to a first HARQ process and a second transport block corresponding to a second HARQ process, in a case that the HARQ indicator included in the transmitted PHICH indicates the NACK, a non-adaptive retransmission of the first transport block corresponding to the first HARQ process is performed by the terminal device in a 4th subframe after a subframe in which the HARQ indicator is transmitted, in a case that a transmission of the second transport block corresponding to the second HARQ process is scheduled by the uplink grant, the transmission of the second transport block is performed by the terminal device in a 3rd subframe after a subframe in which the uplink grant is transmitted, and in a case that a transmission of the first transport block corresponding to the first HARQ process collides with the transmission of the second transport block corresponding to the second HARQ process, not expecting to receive any further retransmissions of the first transport block corresponding to the first HARQ process.
 12. The integrated circuit according to claim 11, the integrated circuit causing the base station apparatus to perform: allowing the uplink grant to be transmitted in a UE-specific search space. 